In the field of manufacturing of semiconductor devices, spin coating is used at forming coating films such as photoresist films or protective films to apply coating materials to coating objects. At the spin coating, coating material is applied to the center of a coating object fixed on a stage, and then the stage is rotated at high speed. The coating material on the coating object is spread over the entire surface of the coating object by centrifugal force, thus forming a coating film.
However, the coating material scatters at the spin coating, and the use efficiency of the material is as low as about 30%. Accordingly, there is a proposition of a spiral coating method which applies the coating material to the coating object in a spiral fashion to increase the use efficiency of the coating material.
However, the spiral coating has a problem of uneven thickness of the coating film formed on the coating object. Specifically, at the spiral coating, the application nozzle is moved in such application intervals that adjacent parts of the coating material overlap on the coating object. This causes unevenness in thickness of the coating film (hereinafter, referred to as coating pitch unevenness) in such a manner that the thickness of the coating film periodically changes at the coating pitch. Even if the coating material is arranged at regular intervals on the coating object, the coating pitch unevenness is similarly caused. Moreover, the circumferential speed is zero at the center of the coating object from which the coating starts. The coating film is therefore thick at the center thereof (hereinafter, starting point unevenness). Furthermore, the coating material dries quickly in the periphery of the coating film. Accordingly, there is a tendency of the coating film to include protrusions (a crown).